Perlin Noise Generation not functioning properly

Question

I have been working with perlin noise recently and when implementing it into a tile engine I am using, I have noticed that the perlin noise function produced "blocks" as seen in the picture below. Each pixel is another different location in a 500 by 500 array that is returned from the perlin noise function.

in this example the persistence is 0.5 with an octave count of 5

When playing with it further, the more octaves I have, the larger the block chunks.

Here is the Code that I am using to call the perlin noise function:

PerlinNoise p = new PerlinNoise();
//returns a float[][] array of 500 by 500
p.GeneratePerlinNoise(p.genWhiteNoise(500, 500), 5, (float) 0.1);

PerlinNoise class

import java.util.Random;

public class PerlinNoise {
Random r;

public PerlinNoise() {
    r = new Random();
}

public void setSeed(long seed) {
    r.setSeed(seed);
}

public void printOutArray(float[][] arr) {
    for(int i = 0; i < arr.length; i++) {
        for(int n = 0; n < arr[0].length; n++) {
            System.out.print(arr[i][n] + ", "); 
        }
        System.out.print("\n");
    }
}

public void printOutTerrain(float[][] arr) {
    for(int i = 0; i < arr.length; i++) {
        for(int n = 0; n < arr[0].length; n++) {
            float a = arr[i][n];
            if(a < 0.4) {
                System.out.print("W"); 
            } else {
                System.out.print("L"); 
            }
        }
        System.out.print("\n");
    }
}

//-------------------------------------------------------------//

float[][] genWhiteNoise(int width, int height) {
    float[][] noise = new float[height][width];

    for(int y = 0; y < height; y++) {
        for(int x = 0; x < width; x++) {
            noise[y][x] = r.nextFloat();
        }
    }

    return noise;
}

float[][] genSmoothNoise(float[][] baseNoise, int octave) {
    int height = baseNoise.length;
    int width = baseNoise[0].length;

    float[][] smoothNoise = new float[height][width];

    int samplePeriod = 1 << octave; //calculates 2^k
    float sampleFrequency = (float) (1.0/samplePeriod);

    for(int i = 0; i < height; i++) {
        int sample_i0 = (i / samplePeriod) * samplePeriod;
        int sample_i1 = (sample_i0 + samplePeriod) % height; //wrap around
        float vertical_blend = (i - sample_i0) * sampleFrequency;

        for(int n = 0; n < width; n++) {
            int sample_n0 = (n / samplePeriod) * samplePeriod;
            int sample_n1 = (sample_n0 + samplePeriod) % width; //wrap around
            float horizontal_blend = (n - sample_n0) * sampleFrequency;

            //blend the top two corners
            float top = Interpolate(baseNoise[sample_i0][sample_n0],
                baseNoise[sample_i1][sample_n0], horizontal_blend);

            //blend the bottom two corners
            float bottom = Interpolate(baseNoise[sample_i0][sample_n1],
                baseNoise[sample_i1][sample_n1], horizontal_blend);

            //final blend
            smoothNoise[i][n] = Interpolate(top, bottom, vertical_blend);
        }
    }

    return smoothNoise;
}

float[][] GeneratePerlinNoise(float[][] baseNoise, int octaveCount, float persistance)
{
   int height = baseNoise.length;
   int width = baseNoise[0].length;

   float[][][] smoothNoise = new float[octaveCount][][]; //an array of 2D arrays containing

   //generate smooth noise
   for (int i = 0; i < octaveCount; i++)
   {
       smoothNoise[i] = genSmoothNoise(baseNoise, i);
   }

    float[][] perlinNoise = new float[height][width];
    float amplitude = 1.0f;
    float totalAmplitude = 0.0f;

    //blend noise together
    for (int octave = octaveCount - 1; octave >= 0; octave--)
    {
       amplitude *= persistance;
       totalAmplitude += amplitude;

       for (int i = 0; i < height; i++)
       {
          for (int j = 0; j < width; j++)
          {
             perlinNoise[i][j] += smoothNoise[octave][i][j] * amplitude;
          }
       }
    }

   //normalisation
   for (int i = 0; i < height; i++)
   {
      for (int j = 0; j < width; j++)
      {
         perlinNoise[i][j] /= totalAmplitude;
      }
   }

   return perlinNoise;
}

//linear average between two points
float Interpolate(float x0, float x1, float alpha)
{
    return Cosine_Interpolate(x0, x1, alpha);
}

//Linear Interpolation
float Linear_Interpolate(float x0, float x1, float alpha)
{
    return x0 * (1 - alpha) + alpha * x1;
}

//Cosine interpolation (much smoother)
float Cosine_Interpolate(float x0, float x1, float alpha)
{
    float ft = (float) (alpha * 3.141592653589);
    float f = (float) ((1 - Math.cos(ft)) * 0.5);

    return x0*(1-f) + x1*f;
}


}

So to reiterate my question: Why is my perlin noise function behaving the way it does, as in only generating space in chunks?

Answer 1

So to fix this, all I had to do is swap the vertical_blend and horizontal_blend variables in the genSmoothNoise() method. It's amazing what you notice after a break